GB2105810A

GB2105810A - Device for the automatic variation of the stroke of a crank mechanism

Info

Publication number: GB2105810A
Application number: GB08219913A
Authority: GB
Inventors: Kalus Wedler
Original assignee: Croon and Lucke Maschinenfabrik GmbH and Co KG
Current assignee: Croon and Lucke Maschinenfabrik GmbH and Co KG
Priority date: 1981-08-17
Filing date: 1982-07-09
Publication date: 1983-03-30
Also published as: DE3132320A1; IT8222128A1; IT8222128A0; GB2105810B; ES513647A0; JPS5842821A; IT1151966B; ES8305103A1; FR2511462A1

Abstract

A crank mechanism has a crank arm (4) disposed transversely on a drive crankshaft (2) and a crankpin (5) which projects from the crank arm and is arranged to be connected to a member to be driven. A device for automatically varying the stroke of the crank mechanism includes a slide guide (7,8) in which the crankpin (5) is guided. A screw spindle (11) is disposed parallel to and to be rotatable with the crank arm (4) and is arranged to adjust the crankpin in the slide guide radially relative to the crankshaft (2). The end of the screw spindle (11) facing the crankshaft is rotationally fixed to a first bevel gear (12) which meshes with a second bevel gear (24) mounted for free rotation on the crankshaft. The second bevel gear (24) is driven by the crankshaft (2) through a transmission train (13,14, 22,23) at a speed different from that of the crankshaft (2). <IMAGE>

Description

SPECIFICATION Device for the automatic variation of the stroke of a crank mechanism The invention relates to a device for the automatic variation of the stroke of a crank mechanism comprising a crank arm disposed transversely on a driven crankshaft and a crankpin which projects from the crank arm and is arranged to be connected two a member to be driven.

A crank mechanism of this kind generally drives, through a connecting rod pivoted on the crankpin, a member making a reciprocating movement in a slide guide, the linear stroke path of this member being determined by the radius of the orbit circle of the crankpin. Crank mechanisms of this kind are used with particular advantage in reeling machines in the textile industry. In these machines threads or yarns are wound to form a skein on a reel cage, the threads or yarns being wound side by side in a determined width and in a plurality of layers lying one above the other It is important in this process that layers of thread or yarn wound later should have a smaller width, so that the cross-section of the skein as a whole is trapezoidal in shape.The various winding widths are determined by a thread guide which is driven in a reciprocating movement and whose stroke path must be continuously shortened during the skein winding operation in order to achieve the previously mentioned trapezoidal cross-section of the skein. If a reciprocating thread guide of this kind is driven by a crank mechanism with the aid of a connecting rod or similar linkage, it is necessary for the radial distance between the crankpin and the crankshaft to be varied automatically and as constantly as possible.

It is an object of the invention to provide a crank mechanism in which the distance between the crankshaft and the crankpin can be automatically varied during the rotation of the crank.

According to the invention, a device for automatically varying the stroke of the crank mechanism comprises a slide guide in which said crankpin is guided, a screw spindle disposed parallel to and rotatable with the crank arm and arranged to adjust the crankpin in the slide guide radially relative to the crankshaft, first transmission means rotationally fixed to an end of the screw-spindle facing the crankshaft, second transmission means engageable with the first transmission means and mounted for free rotation on the crankshaft, and a transmission between the crankshaft and said second transmission means arranged to drive the second transmission means at a speed different from that of the crankshaft.

An embodiment of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: Figure lisa side view, partly in section of a device for the automatic variation of the stroke of a crank mechanism, and Figure 2 is a front view of the device taken in the direction of the arrow A of Figure 1.

The drawings illustrate a crank mechanism comprising a crankshaft 2 which is driven by a trasmission or motor 1 and to which a crank arm 4 is rotationally fixed by a threaded bolt 3 at the end face of the crankshaft. The crank arm 4 extends radially relative to the crankshaft 2 and carries a crankpin 5.

This crankpin is connected in a manner known per se, and therefore not illustrated, to a member which is to be reciprocably driven. For example, the crankpin 5 may be connected by a connecting rod to the thread guide of a reeling machine to reciprocate the thread guide in a slide guide. A reeling machine of this kind, in which the crank mechanism of the invention may be used with particular advantage, is designated 10 in the drawings. The motor 1 is mounted on the reeling machine 10 in a fixed position.

As illustrated, the crankpin 5 is mounted on a sliding member 6, which is slidable in a slide guide formed by two rails 7,8 radially relative to the crankshaft 2. The sliding member 6 has a threaded through bore 9, into which a screw spindle 11 is screwed. The screw spindle 11 is rotatably mounted in the crank arm 4 between the rails 7,8. At its end facing the crankshaft 2 the screw spindle 11 is rotationally fixed to a first bevel gear 12. Since the sliding member 6 and consequently also the crankpin 5 are held non-rotatably in the slide guide formed by the rails 7,8, the radial distance between the crankshaft 2 and the crankpin 5 can be varied by rotation of the bevel gear 12.

In the crank mechanism the distance between the crankshaft 2 and the crankpin 5 can automatically varied during the rotation of the shaft 2. To achieve this, a first gear 13 is mounted on and fixed for rotation with the crankshaft 2, and meshes with a second gear 14 having the same diameter and same number of teeth. Thus, the two gears 13 and 14 rotate at the same speed, that is, have a transimission ratio of 1:1. A shaft 17 is supported in bearings 15,16 which are fixed in position, and in the illustrated embodiment the second gear 14 is mounted for free rotation on this shaft 17. A remotely controlled clutch 18, for example an electromagnetic clutch, is mounted with one part 19 on the shaft 17 so as to rotate with the shaft 17. The other part 21 of the clutch is fixed for rotation with the gear 14.When the clutch 18 is engaged, the gear 14 and the shaft 17 can be rotationally fixed to one another. In addition, a third gear 22 is rotationally fixed to the shaft 17 and in the turn meshes with a fourth gear 23, which is mounted for free rotation on the crankshaft 2 and is rotationally fixed to a second bevel gear 24. The bevel gear 24 is likewise mounted for free rotation on the crankshaft 2, and is coaxial with the crankshaft 2. As illustrated, the second bevel gear 24 meshes with the first bevel gear 12.

To achieve relative rotation between the crankshaft 2 and the bevel gear 24, and thus to enable the bevel gear 12 to be driven, the tranmission ratio of the two gears 22 and 23 is slightly different from that of the gears 13 and 14. In the embodiment described, one of the gears 22 or 23 may have 100 teeth and the other 99 teeth. The transmission ratio of the bevel gears 12 to 24 may, for example, be 5 3.

When the crankshaft 2 is constantly rotated by the motor 1, as the transmission ratio of the gears 22 and 23 is slightly different from 1: 1, the second bevel gear 24 drives the first bevel gear 12 and therefore also the screw spindle 11, so that the crankpin 5 is continuously displaced radially. In this way a crank mechanism is obtained whoe stroke is automatically and continuously variable and which, as previously stated, is particularly advantageous for driving thread guides in reeling machines in which it is desired to produce yarn or thread skeins of trapezoidal cross-section.

As also shown in the drawings, the gear 22 meshes constantly with the drive pinion 25 of a motor 26, which is mounted in a fixed position on the machine frame and which, like the motor 1, is preferably an electric motor. This motor 26 runs without load, that is without voltage, in normal operation of the crank mechanism, that is, for example, during a skein winding operation. The motor 26 is used to return the crankpin 5 to the starting position. For this purpose, while the crankshaft is rotating or stationary, the clutch 18 is disengaged, so that the shaft 17 is no longer driven by the gear 14.The motor 26 is then switched on, so that the crank pin 5 is returned to its starting position by means of the gears 22 and 23 and the bevel gears 24 and 12 at a substantially higher speed than the speed of movement of this crankpin during normal operation, that is to say for example during the winding of a skein.

In order to fix the operating position of the crankpin 5, and in particular to ensure that the crankpin 5 reaches its starting position, a counter 27 is provided, which is schematically indicated Figure 1. The counter 27 counts the rotations of the shaft 17, and in a reeling machine of the customary type indicates a number of revolutions, for example, 3,500 revolutions after a running time of about 30 minutes. The crankpin 5 is returned to its starting position by the motor 26 in the manner previously described, until the counter 27 has reached zero again. When the counter 27 reaches the reading zero it switches off the motor 26 in a manner known per se.

In customary reeling machines the stroke of the thread guide is gradually shortened by about 25 mm in order to obtain the previously mentioned trapezoidal cross-section of the skein. The crankpin 5 is also moved the same distance, which means that the screw spindle 11 may make only a few turns for several thousand rotations of the crankshaft. Large reduction ratios are normally necessary for this purpose, and cannot be achieved in a small space.

The invention overcomes this difficulty in a manner illustrated by an elegant solution.

With the device illustrated and described it is also possible for the movement of the crankpin 5 on the crank arm 4to be controlled discontinuously and non-uniformlywhen the clutch 18 is disengaged and the motor 26 is used as a control motor. Depending on the running time and speed of the motor 26, the crankpin 5 then makes during the rotation of the crank determined movements, which for example are used for producing skeins of yarn on winding cores which have a cross-section differing from the trapezoidal shape. Here again the counter 27 can be used for detecting the various positions of the crankpin 5.

The device according to the invention is therefore not only suitable for continuous automatic variation of the stroke in a crank mechanism, whereby a radial displacement of the crankpin proportional to the rotations of the crank is achieved.

In the embodiment of the invention the transmission comprises gears including the bevel gears 12 and 24. Of course, other types of transmissions may be used, for example, cogged belt wheels or chain wheels connected together by cogged belts or chains may be provided.

Instead of being disposed between the shaft 17 and the transmission wheel 14, the clutch 18 could also lie between the shaft 17 and the transmission wheel 22.

Claims

1. A device for automatically varying the stroke of a crank mechanism having a driven crankshaft, a crank arm disposed transversely on the crankshaft, and a crankpin projecting from the crank arm and arranged to be connected to a member to be driven, said device comprising a slide guide in which said crankpin is guided, a screw spindle disposed parallel to and rotatable with the crank arm and arranged to adjust the crankpin in the slide guide radially relative to the crankshaft, first transmission means rotationally fixed to an end of the screw spindle facing the crankshaft, second transmission means engageable with the first transmission means and mounted for free rotation on the crankshaft, and a transmission between the crankshaft and said second transmission means arranged to drive the second transmission means at a speed different from that of the crankshaft.

2. A device as claimed in Claim 1, wherein the transmission between the crankshaft and said second transmission means comprises a first transmission wheel rotationally fixed to the crankshaft, a second transmission wheel arranged to be driven by said first transmission wheel with a transmission ratio of 1:1, a third transmission wheel fixed for rotation with the coaxial to said second transmission wheel, and a fourth transmission wheel fixed for rotation with and coaxial to said second transmission means, wherein the third transmission wheel is arranged to drive said fourth transmission wheel with a transmission ratio different from 1:1.

3. A device as claimed in Claim 2, wherein a common shaft extends parallel to the crankshaft and the second and third transmission wheels are mounted on said common shaft, and one of the second and third transmission wheels is detachably connected by a clutch to said common shaft.

4. A device as claimed in Claim 2 or 3, further comprising a motor arranged to rotate the third or fourth transmission wheel for the radial return of the crankpin.

5. A device as claimed in Claim 4, further comprising a counter for counting the rotations of the common shaft and arranged to switch off the motor after the return of the crankpin.

6. A device as claimed in any of Claims 2 to 4, characterised in that the transmission wheels are in the form of gears, cogged belt wheels, or chain wheels.

7. A device according to Claim 1 or Claim 2, wherein said first and second transmission means are first and second bevel gears.

8. A device for automatically varying the stroke of a crank mechanism substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.